A closed door.

An open door.

Doors allow passage from one room to a neighboring room. Agents, rescued Couriers or Prisoners, and guards can all open and close doors. When closed, doors are impassable and provide hard cover.

Agency controlled units can open and close doors when orthogonally or diagonally adjacent to them; guards can only open and close doors when orthogonally adjacent to them. In addition, agents can install Shock Traps on all kinds of doors when orthogonally adjacent to them.

Usually, when agents or rescued Couriers or Prisoners open or close doors that guards can see, the guard will notice the door opening or closing on the side it was opened or closed on. This will happen even if the tile the door is adjacent to is in soft cover, as doors do not receive soft cover. Hacked drones and Archive Prism in disguise can open and close doors without causing guards to be interested.

Human guards, when not alerted, will usually leave doors in the condition they were in after they move through them. The only exception is when they open a door to perform a peek or when they are KOed, killed, or alerted before they have the chance to close the door. Drones and all alerted guards will always leave doors open when moving through them.

Guards, when alerted, can in some conditions destroy closed doors, rendering them permanently open and dealing 1 KO damage to any unit on the other side. Agents, Couriers or Prisoners KOed in this way will also start the next turn with 0 AP if they were not pinned before waking up. This can only happen when the guard's interest point is one tile beyond the door from the guard, and it usually happens because the guard noticed an agent close it. An Akuma Drone can also be hacked to “kick” down doors as well.

A locked Lvl1 Security Door.

Lvl1 Security Doors are doors that cannot be opened until they are unlocked by a Lvl1 Security Passcard, Banks's Crypto Computer, or a Lock Decoder after 2 turns. Guards cannot unlock these doors, nor will they try to path through them until they are unlocked. Banks can unlock the doors when she is either orthogonally or diagonally adjacent to them. The Lock Decoder can be placed only by an agent who is standing orthogonally adjacent to the doors.

Note that with the exception of the Lvl1 Security Door that guards the Secure Locker in Security Dispatch missions, there is always an alternate route to the other side of a Lvl1 Security Door.

A Vault Door.

Vault Doors are doors that cannot be opened until they are unlocked by a Vault Access Card. They will only appear in Vault missions and some Cybernetics Lab missions. They will always be found in the Objective rooms of these missions, and need to be unlocked and opened to access additional loot.

Exit Doors cannot be opened until they are unlocked by a Exit Access Card. They appear in Endless modes from day 5 onwards, in all facilities. Unlocking the Exit Door is required to reach the exit room and complete the mission.

Two guard entrance doors block the way to guard entrance rooms. These doors cannot be opened by agency-controlled units, and automatically close once guards pass through them, even if a guard would not normally close a door in that situation. As such, it is not normally possible for an agent to enter guard entrances.

It is possible to set up a Shock Trap on these doors.

Navigating between rooms of a facility is a core part of Invisible Inc.'s gameplay. Doors are the most common bottlenecks in Invisible Inc., both for vision and for navigating the facility, so a lot of Invisible Inc.'s strategy comes down to using doors effectively - maximizing your vision and mobility, and minimizing that of the guards.

The best strategy for the player depends heavily on what game mode you are on. When playing a higher difficulty than you are used to, you may need to unlearn strategies that worked on lower difficulties.

• When opening a door to a new area, it is almost always right to either peek through it first or open it from a tile diagonally adjacent to it. Otherwise, you run the risk of being immediately seen by a Security Camera or guard.
• It's a good habit to always close doors after moving through them, as doors left open can leave unexpected sight lines for guards to see your agents later. Random doors being open tends to favor the guards over the player. There are a few exceptions, primarily in situations when a guard will notice the door being closed, but closing the door should be the default option.
• If a guard sees the door you're about to open, consider waiting until next turn to open it - he may patrol away, allowing you to open it undetected next turn. Simply opening the door (from a diagonally adjacent tile), luring the guard in, and KOing him is also a viable option, but it is better to avoid disturbing the guard at all.
• If no guard sees the door you're about to open, you can freely open the door and then peek again to get a more complete picture of the next room, and allow you to hack mainframe devices there.
  • On difficulties below Expert Plus, you can be sure no guard will notice the door if the tile in front of it is not “Watched”, “Noticed”, or “Hidden”.
• If you decide to open the door to lure a guard in for an ambush, you have two options:
  • 1) Stand in front of the door for the ambush.
    • The advantage of this is that even if the guard sees other agents when opening the door, they will be KOed before they can react.
    • Do not stand in front of the door if the guard is alerted! This will result in the guard kicking the door down and KOing your ambushing agent. Depending on how the guard is coming in and what cover is available next to the door, it may be possible to ambush alerted guards in this way by leaving the door open.
    • This method also runs a higher risk of another guard seeing the lured guard be knocked out than the other method. If this happens, the witnessing guard becomes alerted. In addition, since you're right in front of the door, it's quite likely he overwatches you this turn.
  • 2) Stand diagonally adjacent to the door for the ambush
    • You will need to ensure that no agents are immediately visible when the guard opens the door; otherwise the guard will overwatch them before falling for the trap.
    • There are not as many sight lines for another guard to see the lured guard be knocked out, and even if they do, they're much less likely to overwatch the ambushing agent since they're in cover.
• In some worst-case-scenarios, it can be worth it to be deliberately be overwatched by a guard through a door. Though being overwatched is always dangerous, being overwatched through a door is less dangerous than other situations, as the guard's vision into your room can be limited, allowing plenty of options for escape. In addition, the door can often just be closed to escape.
  • You can even use the fact that guards will not move after overwatching to use a door as a chokepoint in certain conditions - if a guard can see an agent before moving through a door, they will not move through the door. The developers gave guards the ability to kick down doors to make these kinds of tactics less effective, but this can often be circumvented by distracting the guards after closing the door using methods such as sprinting, causing them to not kick the door down.

On Experienced and higher difficulty, guards will have longer patrols that often go through a door, and they can patrol into the Starting room. This makes doors more dangerous to the player than on Beginner.

• On turn 1, your first task in the mission is to assess how to protect your agents from being seen by guards any guards entering the Starting room. This can be done by using cover, ambushing, or sometimes with early exploration. If you have enough AP to do so, peeking into the next room(s) is a good idea, though you should have a plan if the door is not safe to open. If no guards enter the Starting room on the first turn, it's (probably) patrol-free, and you can use AP more liberally.
• When peeking into a room for the first time, it's a good idea to maintain the peek through the door through the corporation's turn to observe the room for a full turn. This will allow you to know whether there are any guards who patrol through doors into that room.

On Expert Plus, you can no longer be sure that a door is not seen by a guard when peeking through it while closed.

This means that you will always need to account for the possibility that a stationary guard is watching the door, even if you peek through it and listen for patrols. Because of this, on Expert Plus, you should avoid opening doors unless you are able to account for this possibility, even with a peek through the door. As a result, if you can account for this possibility, it can often be better to open the door (from a diagonally adjacent tile) without peeking, peek with the door open, then (if noticed) get to safety.